Method for locating a bottleneck in a radio communication network

ABSTRACT

The present disclosure relates to a method performed in a Radio Access Network (RAN) comprised in a communication network, for locating a communication bottleneck in said communication network. The method comprises estimating a first Round Trip Time (RTT) between the RAN and a terminal device connected via the RAN. The method also comprises estimating a second RTT between the RAN and a server of a service provider configured for providing a service to the terminal device via the RAN. The method also comprises estimating an end-to-end RTT between the terminal device and server, based on the first and second RTT. The method also comprises determining a relative contribution of the second RTT to the end-to-end RTT. The method also comprises determining that the relative contribution of the second RTT indicates that signalling performance between the server and terminal device is limited by the signalling performance between the server and RAN.

TECHNICAL FIELD

The present disclosure relates to a method for locating a communicationbottleneck in a radio communication network.

BACKGROUND

End user experience or Quality of Experience (QoE) is a differentiatorfor mobile operators and internet service providers. Applications areincreasingly attempting to adapt to ensure a good QoE. For example,Adaptive Bit Rate video adapts the required throughput by changing mediarate by using an encoded video format with a suitable bitrate. Currentlythis is done by trying to estimate the throughput between the serviceprovider server and the application (app) in the client (e.g. in a UserEquipment, UE), e.g. based on measured link bit rate or round trip time(RTT). How frequently the bitrate can be changed varies. A typicalinterval for adaptive video streaming would be every 2-5 seconds.

Feedback of available throughput from Radio Access Network (RAN) nodesto nodes outside of the RAN is being discussed (e.g. in Third GenerationPartnership Project (3GPP), Institute of Electrical and ElectronicsEngineers (IEEE), and Internet Engineering Task Force (IETF) proposals)to improve end user QoE.

In the IETF informal internet draft, “Requirements and referencearchitecture for Mobile Throughput Guidance Exposure” by A. Jain et al.19 Feb. 2015, a throughput guidance is sent from the mobile network to aTransmission Control Protocol (TCP) server. The idea is to have aThroughput guidance provider residing in the RAN, which feeds the TCPserver periodically with estimated throughput in downlink per UE or perflow. Regarding the accuracy of the throughput guidance it is statedthat the throughput guidance should be treated only as an estimate tothe optimization algorithm running at the TCP server. The TCP serverthat receives this information should not assume that it is alwaysaccurate and up to date. Specifically, the TCP server should check thevalidity of the information received and if it finds it erroneous itshould discard it and possibly take other corrective actions (e.g.,discard all future throughput guidance information from a particularInternet Protocol (IP) prefix).

SUMMARY

In Transmission Control Protocol (TCP) end-points, the total availableend-to-end throughput is estimated through RTT measurements. To improvethe TCP performance, it could be proposed to use throughput estimationsfrom the RAN to adjust the TCP behaviour.

A possibility would be to introduce an interface for interaction betweenthe service provider server and the mobile/operator network of acommunication network, for improving the QoE of the end-user. Anadditional possibility would be to also introduce an interface forinteraction between the client (in a radio device, e.g. UE or otherterminal device) and the mobile/operator network, for improving the QoEof the end-user. Such an interface between the mobile/operator networkand a terminal device could include an interaction gateway (IGW) in thenetwork side (typically in the RAN or uplink of the Packet Data Network,PDN, Gateway (PGW), e.g. in the SGi interface, in the network). By meansof the IGW, control information may be sent between the app (acting as aservice client) in the terminal device and the mobile/operator network(e.g. the RAN thereof) via user plane communication/bearers, which maybe advantageous since the app typically has no access to control planebearers between the terminal device and the RAN.

One example use case for interaction by means of the IGW is networkassistance (which aims to improve QoE), where the client in the terminaldevice sends a query message to the RAN node asking for the availablebitrate. This query is handled by the IGW which interacts with afunction for recommendation, and an achievable bit rate isestimated/predicted for the terminal device. Then, a response message issent back to the terminal device. The achievable bitrate depends on anumber of factors, e.g. number of terminal devices/UEs in the cellserved by the RAN node that needs to share the capacity, the radioconditions of the terminal device, and the priority for the bearerdedicated to the service.

Since a 3GPP RAN node decides the resource allocation for each bearer,the RAN node is also capable of telling the available throughput foreach bearer. This information could be useful for end-points, such asthe terminal device and/or the server, since this this information couldbe used to determine how/what data to send to maximize end-user QoE.However, if the available throughput in the RAN is not limiting (i.e. abottleneck is outside of the RAN), the information about availablethroughput in the RAN is less useful in order to optimize end-to-endQoE.

Thus, a problem with the above discussed solution with an IGW is thateven if available throughput in RAN is fed back to the end-point e.g.the video client app or TCP server, the end-point cannot be sure thatthe RAN is limiting the end-to-end throughput (i.e. comprises thebottleneck). There is currently no method for the end-point to determinethe relevance of the information of available throughput in the RAN. Thebottleneck may be the back-haul transport network or the server/ContentDistribution Network (CDN) itself. This implies that the end point isnot sure that an action based on information about available throughputin the RAN would lead to improved end-to-end QoE since this depends onwhether the RAN is the bottleneck or not.

In the present disclosure, it is proposed that, possibly in addition toinformation about available throughput (or congestion situation) in theRAN, information about the RAN addition to packet delay is determined inorder to locate the bottleneck. This information could be used todetermine the relevance of the information about available throughput inthe RAN. The information may either be sent to terminal device, or beused by the RAN itself. With this bottleneck information, in relation toestimations of total end-to-end delay or RTT, a more correct decisionabout how to utilize the information about the throughput estimations inRAN could be made. Also in other use cases, information about thelocation of a bottleneck may be relevant.

According to an aspect of the present disclosure, there is provided amethod performed in a RAN comprised in a communication network, forlocating a communication bottleneck in said communication network. Themethod comprises estimating a first RTT between the RAN and a terminaldevice connected via the RAN. The method also comprises estimating asecond RTT between the RAN and a server of a service provider configuredfor providing a service to the terminal device via the RAN. The methodalso comprises estimating an end-to-end RTT between the terminal deviceand the server, based on the first RTT and the second RTT The methodalso comprises determining a relative contribution of the second RTT tothe end-to-end RTT. The method also comprises determining that therelative contribution of the second RTT indicates that signallingperformance between the server and the terminal device is limited by thesignalling performance between the server and the RAN. This would thusimply that the bottleneck is not in the RAN but higher up in thecommunication network, e.g. in the Core Network (CN) of the operatornetwork, in the PDN such as the Internet, or in the CDN (comprising theserver) of the service provider.

According to another aspect of the present disclosure, there is provideda computer program product comprising computer-executable components forcausing a RAN node to perform an aspect of the method of the presentdisclosure when the computer-executable components are run on processorcircuitry comprised in the RAN node.

The method may be performed by a RAN node, e.g. a Node B or an evolvedNode B (eNB), e.g. configured by means of the computer program productmentioned above. Thus, according to another aspect of the presentdisclosure, there is provided a RAN node for a communication network,configured for locating a communication bottleneck in said communicationnetwork. The RAN node comprises processor circuitry, and storage storinginstructions executable by said processor circuitry whereby said RANnode is operative to estimate a first RTT between the RAN node and aterminal device connected via the RAN node. The RAN node is alsooperative to estimate a second RTT between the RAN node and a server ofa service provider configured for providing a service to the terminaldevice via the RAN node. The RAN node is also operative to estimate anend-to-end RTT between the terminal device and the server, based on thefirst RTT and the second RTT. The RAN node is also operative todetermine a relative contribution of the second RTT to the end-to-endRTT The RAN node is also operative to determine that the relativecontribution of the second RTT indicates that signalling performancebetween the server and the terminal device is limited by the signallingperformance between the server and the RAN.

According to another aspect of the present disclosure, there is provideda computer program for locating a communication bottleneck in acommunication network comprising a RAN. The computer program comprisescomputer program code which is able to, when run on processor circuitryof a RAN node, cause the RAN node to estimate a first RTT between theRAN node and a terminal device connected via the RAN node. The code isalso able to cause the RAN node to estimate a second RTT between the RANnode and a server of a service provider configured for providing aservice to the terminal device via the RAN node. The code is also ableto cause the RAN node to estimate an end-to-end RTT between the terminaldevice and the server, based on the first RTT and the second RTT. Thecode is also able to cause the RAN node to determine a relativecontribution of the second RTT to the end-to-end RTT. The code is alsoable to cause the RAN node to determine that the relative contributionof the second RTT indicates that signalling performance between theserver and the terminal device is limited by the signalling performancebetween the server and the RAN.

According to another aspect of the present disclosure, there is provideda computer program product comprising an embodiment of the computerprogram of the present disclosure and a computer readable means on whichthe computer program is stored.

It is to be noted that any feature of any of the aspects may be appliedto any other aspect, wherever appropriate. Likewise, any advantage ofany of the aspects may apply to any of the other aspects. Otherobjectives, features and advantages of the enclosed embodiments will beapparent from the following detailed disclosure, from the attacheddependent claims as well as from the drawings.

Generally, all terms used in the claims are to be interpreted accordingto their ordinary meaning in the technical field, unless explicitlydefined otherwise herein. All references to “a/an/the element,apparatus, component, means, step, etc.” are to be interpreted openly asreferring to at least one instance of the element, apparatus, component,means, step, etc., unless explicitly stated otherwise. The steps of anymethod disclosed herein do not have to be performed in the exact orderdisclosed, unless explicitly stated. The use of “first”, “second” etc.for different features/components of the present disclosure are onlyintended to distinguish the features/components from other similarfeatures/components and not to impart any order or hierarchy to thefeatures/components.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will be described, by way of example, with reference to theaccompanying drawings, in which:

FIG. 1 is a schematic illustration of an embodiment of a communicationnetwork in accordance with the present disclosure.

FIG. 2 is a schematic block diagram illustrating estimated RTT in anembodiment of the communication network in accordance with the presentdisclosure.

FIG. 3a is a schematic block diagram of an embodiment of a RAN node inaccordance with the present disclosure.

FIG. 3b is a schematic functional block diagram of an embodiment of aRAN node in accordance with the present disclosure.

FIG. 4 is a schematic illustration of an embodiment of a computerprogram product in accordance with the present disclosure.

FIG. 5a is a schematic flow chart of an embodiment of a method inaccordance with the present disclosure.

FIG. 5b is a schematic flow chart of another embodiment of a method inaccordance with the present disclosure.

DETAILED DESCRIPTION

Embodiments will now be described more fully hereinafter with referenceto the accompanying drawings, in which certain embodiments are shown.However, other embodiments in many different forms are possible withinthe scope of the present disclosure. Rather, the following embodimentsare provided by way of example so that this disclosure will be thoroughand complete, and will fully convey the scope of the disclosure to thoseskilled in the art. Like numbers refer to like elements throughout thedescription.

FIG. 1 is a schematic overview of a communication network 1 comprising aRAN 2, e.g. of an operator network also comprising a Core Network (CN) 5via which the RAN offers connection to a PDN 7, such as the Internet.The RAN 2 may be any type of RAN such as a cellular RAN or a WirelessLocal Area Network (WLAN) RAN, but may typically be a cellular RAN inaccordance with a 3GPP standard, such as Long Term Evolution (LTE). TheRAN comprises one or a plurality of base stations 3, e.g. a Node B or anevolved Node B (eNB). The RAN 2 serves one or a plurality of terminaldevice(s) 4 and offers data connection to the PDN 7 for the terminaldevice(s) 4. The terminal device 4 may be connected directly to a basestation 3 of the RAN 2, or be, e.g. a tethering device, connected viaanother radio device which is connected directly to the base station 3.The terminal device 4 may be any device or user equipment (UE), mobileor stationary, enabled to communicate over a radio channel in thecommunication network 1, for instance but not limited to e.g. mobilephone, smartphone, modem, sensors, meters, vehicles (e.g. a car),household appliances, medical appliances, media players, cameras, or anytype of consumer electronic, for instance but not limited to television,radio, lighting arrangements, tablet computer, laptop, or personalcomputer (PC). A server 6, e.g. comprised in a CDN, of a serviceprovider resides in, or is accessible via, the PDN 7. The serviceprovider can provide a service from the server 6 to a service client 8in the terminal device 4. The service client could be a serviceapplication (app) in the terminal device 4, e.g. a smartphone, but couldalso/alternatively be a script in a browser in the terminal device.There may be a service level communication between the service client 8in the terminal device 4 and the server 6 of the service provider. Theclient 8 is thus configured for service level communication with theservice provider, e.g. with the server 6.

FIG. 2 schematically illustrates the first and second RTT, respectively,in the communication network 1. The first RTT is measured/estimatedbetween the RAN 2 and the terminal device 4, e.g. the client 8 in saidterminal device, from the RAN to the terminal device and back again tothe RAN. The second RTT is measured/estimated between the RAN and theserver 6 providing the service of the service provider, from the RAN tothe server and back again to the RAN. Based on the first and second RTT,as estimated, the total (end-to-end) RTT between the terminaldevice/client and the server is estimated, e.g. as the sum of the firstand second RTTs.

FIG. 3a schematically illustrates an embodiment of a RAN node 3 of thepresent disclosure. The RAN node 3 comprises processor circuitry 31 e.g.a central processing unit (CPU). The processor circuitry 31 may compriseone or a plurality of processing units in the form of microprocessor(s).However, other suitable devices with computing capabilities could becomprised in the processor circuitry 31, e.g. an application specificintegrated circuit (ASIC), a field programmable gate array (FPGA) or acomplex programmable logic device (CPLD). The processor circuitry 31 isconfigured to run one or several computer program(s) or software (SW) 41(see also FIG. 4) stored in a storage 32 of one or several storageunit(s) e.g. a memory. The SW 41 may additionally or alternativelycomprise a computer program for configuring the RAN node 3 to perform anembodiment of the method discussed herein. The storage unit is regardedas a computer readable means 42 (see FIG. 4) as discussed herein and maye.g. be in the form of a Random Access Memory (RAM), a Flash memory orother solid state memory, or a hard disk, or be a combination thereof.The processor circuitry 31 may also be configured to store data in thestorage 32, as needed. The RAN node 3 also comprises a communicationinterface 33 comprising a radio interface comprising radio transmitterand radio receiver, which may be combined to form a transceiver or bepresent as distinct units within the RAN node 3.

According to an aspect of the present disclosure, there is provided aRAN node 3 for a communication network 1. The RAN node is configured forlocating a communication bottleneck in said communication network. TheRAN node comprises processor circuitry 31, and storage 32 storinginstructions 41 executable by said processor circuitry whereby said RANnode is operative to estimate a first RTT between the RAN node 3 and aterminal device 4 connected via the RAN node. The RAN node is alsooperative to estimate a second RTT between the RAN node 3 and a server 6of a service provider configured for providing a service to the terminaldevice via the RAN node. The RAN node is also operative to estimate anend-to-end RTT between the terminal device 4 and the server 6, based onthe first RTT and the second RTT. The RAN node is also operative todetermine a relative contribution of the second RTT to the end-to-endRTT. The RAN node is also operative to determine that the relativecontribution of the second RTT indicates that signalling performancebetween the server and the terminal device 4 is limited by thesignalling performance between the server 6 and the RAN 2.

FIG. 3b is a schematic block diagram functionally illustrating anembodiment of the RAN node 3 in FIG. 3a . As previously mentioned, theprocessor circuitry 31 may run software 41 for enabling the RAN node toperform an embodiment of a method of the present disclosure, wherebyfunctional modules may be formed in the RAN node 3 e.g. in the processorcircuitry 31 for performing the different steps of the method. Thesemodules are schematically illustrated as blocks within the RAN node 3.Thus, the RAN node 3 comprises a first RTT estimation module 301 forestimating a first RTT between the RAN node 3 and a terminal device 4connected via the RAN node. The RAN node 3 also comprises a second RTTestimation module 302 for estimating a second RTT between the RAN node 3and a server 6 of a service provider configured for providing a serviceto the terminal device via the RAN node. The RAN node 3 also comprisesan end-to-end RTT estimation module 303 for estimating an end-to-end RTTbetween the terminal device 4 and the server 6, based on the first RTTand the second RTT. The RAN node 3 also comprises a contributiondetermination module 304 for determining a relative contribution of thesecond RTT to the end-to-end RTT. The RAN node 3 also comprises anindication of relative contribution determination module 305 fordetermining that the relative contribution of the second RTT indicatesthat signalling performance between the server and the terminal device 4is limited by the signalling performance between the server 6 and theRAN 2.

In some embodiments, the RAN node 3 also comprises a sending module 306for, based on the determining that the relative contribution of thesecond RTT indicates that signalling performance between the server andthe terminal device 4 is limited by the signalling performance betweenthe server 6 and the RAN 2, sending information to the terminal device 4indicating that the signalling performance between the server 6 and theterminal device 4 is limited by the signalling performance between theserver 6 and the RAN 2.

Additionally or alternatively, the RAN node 3 comprises a sending module306 for, based on the determining that the relative contribution of thesecond RTT indicates that signalling performance between the server andthe terminal device 4 is limited by the signalling performance betweenthe server 6 and the RAN 2, deciding not to send information aboutthroughput between the RAN 2 and the terminal device 4 to the terminaldevice. Such throughput information may be irrelevant to the terminaldevice for deciding on e.g. streaming rate (if the service is astreaming service) since the bottleneck has been determined to bebetween the RAN and the server 6. Thus, the RAN node 3 may activelydecide not to send the throughput information which it would otherwisehave sent to the terminal device.

Alternatively, the modules of FIG. 3b may be formed by hardware, or by acombination of software and hardware.

According to an aspect of the present disclosure, there may be provideda RAN node 3 for a communication network 1. The RAN node is configuredfor locating a communication bottleneck in said communication network.The RAN node comprises means 301 for estimating a first RTT between theRAN 2 and a terminal device 4 connected via the RAN. The RAN node alsocomprises means 302 for estimating a second RTT between the RAN 2 and aserver 6 of a service provider configured for providing a service to theterminal device 4 via the RAN. The RAN node also comprises means 303 forestimating an end-to-end RTT between the terminal device 4 and theserver 6, based on the first RTT and the second RTT. The RAN node alsocomprises means 304 for determining a relative contribution of thesecond RTT to the end-to-end RTT. The RAN node also comprises means 305for determining that the relative contribution of the second RTTindicates that signalling performance between the server and theterminal device 4 is limited by the signalling performance between theserver 6 and the RAN 2.

The RAN node may comprise means 306 for, based on the determining thatthe relative contribution of the second RTT indicates that signallingperformance between the server and the terminal device 4 is limited bythe signalling performance between the server 6 and the RAN 2, sendinginformation to the terminal device 4 indicating that the signallingperformance between the server 6 and the terminal device 4 is limited bythe signalling performance between the server 6 and the RAN 2.

The RAN node may comprise means 306 for, based on the determining thatthe relative contribution of the second RTT indicates that signallingperformance between the server and the terminal device 4 is limited bythe signalling performance between the server 6 and the RAN 2, decidingnot to send information about throughput between the RAN 2 and theterminal device 4 to the terminal device. Such throughput informationmay be irrelevant to the terminal device for deciding on e.g. streamingrate (if the service is a streaming service) since the bottleneck hasbeen determined to be between the RAN and the server 6. Thus, the RANnode 3 may actively decide not to send the throughput information whichit would otherwise have sent to the terminal device.

FIG. 4 illustrates an embodiment of a computer program product 40. Thecomputer program product 40 comprises a computer readable (e.g.non-volatile and/or non-transitory) medium 42 comprisingsoftware/computer program 41 in the form of computer-executablecomponents. The computer program 41 may be configured to cause a RANnode 3, e.g. as discussed herein, to perform an embodiment of the methodof the present disclosure. The computer program may be run on theprocessor circuitry 31 of the RAN node 3 for causing it to perform themethod. The computer program product 40 may e.g. be comprised in astorage unit or memory 32 comprised in the RAN node 3 and associatedwith the processor circuitry 31. Alternatively, the computer programproduct 40 may be, or be part of, a separate, e.g. mobile, storagemeans/medium, such as a computer readable disc, e.g. CD or DVD or harddisc/drive, or a solid state storage medium, e.g. a RAM or Flash memory.Further examples of the storage medium can include, but are not limitedto, any type of disk including floppy disks, optical discs, DVD,CD-ROMs, microdrive, and magneto-optical disks, ROMs, RAMs, EPROMs,EEPROMs, DRAMs, VRAMs, flash memory devices, magnetic or optical cards,nanosystems (including molecular memory ICs), or any type of media ordevice suitable for storing instructions and/or data. Embodiments of thepresent disclosure may be conveniently implemented using one or moreconventional general purpose or specialized digital computer, computingdevice, machine, or microprocessor, including one or more processors,memory and/or computer readable storage media programmed according tothe teachings of the present disclosure. Appropriate software coding canreadily be prepared by skilled programmers based on the teachings of thepresent disclosure, as will be apparent to those skilled in the softwareart.

According to an aspect of the present disclosure, there is provided acomputer program product 40 comprising computer-executable components 41for causing a RAN node 3 to perform an embodiment of the method of thepresent disclosure when the computer-executable components are run onprocessor circuitry 31 comprised in the RAN node.

According to another aspect of the present disclosure, there is provideda computer program 41 for locating a communication bottleneck in acommunication network 1 comprising a RAN 2. The computer programcomprises computer program code which is able to, when run on processorcircuitry 31 of a RAN node 3, cause the RAN node to estimate a first RTTbetween the RAN node 3 and a terminal device 4 connected via the RANnode. The code is also able to cause the RAN node to estimate a secondRTT between the RAN node 3 and a server 6 of a service providerconfigured for providing a service to the terminal device via the RANnode. The code is also able to cause the RAN node to estimate anend-to-end RTT between the terminal device 4 and the server 6, based onthe first RTT and the second RTT. The code is also able to cause the RANnode to determine a relative contribution of the second RTT to theend-to-end RTT. The code is also able to cause the RAN node to determinethat the relative contribution of the second RTT indicates thatsignalling performance between the server and the terminal device 4 islimited by the signalling performance between the server 6 and the RAN2.

According to another aspect of the present disclosure, there is provideda computer program product 40 comprising an embodiment of the computerprogram 41 of the present disclosure and a computer readable means 42 onwhich the computer program is stored.

FIG. 5a is a flow chart of an embodiment of the method of the presentdisclosure. The method is performed in a RAN 2 comprised in acommunication network 1. The method is for locating a communicationbottleneck in said communication network. The method comprisesestimating S1 a first RTT between the RAN 2 and a terminal device 4connected via the RAN. The method also comprises estimating S2 a secondRTT between the RAN 2 and a server 6 of a service provider configuredfor providing a service to the terminal device 4 via the RAN. The methodalso comprises estimating S3 an end-to-end RTT between the terminaldevice 4 and the server 6, based on the first RTT and the second RTT Themethod also comprises determining S4 a relative contribution of thesecond RTT to the end-to-end RTT The method also comprises determiningS5 that the relative contribution of the second RTT indicates thatsignalling performance between the server and the terminal device 4 islimited by the signalling performance between the server 6 and the RAN2.

FIG. 5b is a flow chart of another embodiment of the method of thepresent disclosure. In addition to the steps S1-S5 already discussed inrelation to FIG. 5a , the method may comprise, based on the determiningS5 that the relative contribution of the second RTT indicates thatsignalling performance between the server and the terminal device 4 islimited by the signalling performance between the server 6 and the RAN2, sending S6 information to the terminal device 4 indicating that thesignalling performance between the server 6 and the terminal device 4 islimited by the signalling performance between the server 6 and the RAN2. Thus, the terminal device 4 may be informed about that the bottleneckis likely located between the RAN and the server, why the signallingperformance (e.g. the throughput) between the terminal/client and theserver is limited by the signalling performance between the RAN and theserver.

Additionally or alternatively, the method may also comprise, based onthe determining S5 that the relative contribution of the second RTTindicates that signalling performance between the server and theterminal device 4 is limited by the signalling performance between theserver 6 and the RAN 2, deciding S7 not to send information aboutthroughput between the RAN 2 and the terminal device 4 to the terminaldevice. As discussed above, the RAN may e.g. by means of an IGW, beconfigured to inform the terminal device/client about availablethroughput via the RAN, e.g. for adaptive streaming. However, suchthroughput information may be irrelevant to the terminal device fordeciding on e.g. streaming rate (if the service is a streaming service)since the bottleneck has been determined to be between the RAN and theserver 6. Thus, the RAN node 3 may actively decide not to send thethroughput information which it would otherwise have sent to theterminal device.

An advantage with embodiments of the present disclosure may be that withinformation about the RAN node 3 contribution of end-to-end RTT, therelevance of information about available throughput in the RAN node canbe determined. The actions based on available throughput in RAN couldtherefore be based on how much the RAN node contributes to end-to-endQoE.

In some embodiments of the present disclosure, the first RTT isestimated Si between the RAN 2 and a service client 8 in the terminaldevice 4. It is noted that the RTT measured on service level to theclient 8 is longer than only the radio part. There is delay also withinthe terminal device, from its radio interface to the client (e.g. an appin the application layer of the terminal device) and back to the radiointerface, which is included in the first RTT.

Thus, in some embodiments, the estimating a first RTT comprisesestimating a time from when a communication packet for the serviceclient 8 reaches the RAN 2 to when a response packet, from the serviceclient in response to the communication packet, reaches the RAN. Anydelay within the RAN in the downlink (DL) is thus included in the firstRTT.

Similarly, in some embodiments of the present disclosure, the estimatingS2 a second RTT comprises estimating a time from when a communicationpacket from the terminal device 4, for the server 6, reaches the RAN 2to when a response packet from the server, for the terminal device, inresponse to the communication packet, reaches the RAN. Any delay withinthe RAN in the uplink (UL) is thus included in the first RTT.

In some embodiments of the present disclosure, the determining S5 thatthe relative contribution of the second RTT indicates that signallingperformance between the server and the terminal device 4 is limited bythe signalling performance between the server 6 and the RAN 2 comprisesdetermining that a relative contribution of the first RTT to theend-to-end RTT is below a predetermined first threshold or that therelative contribution of the second RTT is above a predetermined secondthreshold. If the relative contribution of the second RTT is above athreshold, e.g. the second RTT is longer than the first RTT (secondthreshold is 50%) or longer by a predetermined margin than the first RTT(second threshold is higher than 50%), this may indicate that thebottleneck for signalling throughput/bandwidth is between the RAN 2 andthe server 6 rather than between the RAN and the terminal 4. Thus, thesignalling performance (e.g. throughput) between the server and theterminal is assumed to be limited by the signalling performance betweenthe server 6 and the RAN 2. Similarly, since the end-to-end RTTtypically is the sum of the first and second RTTs, the same conclusionmay be drawn if the contribution of the first RTT is below a firstthreshold, e.g. below 50% or below a first threshold which is less than50%. Of course, there may be no direct link between RTT and throughput,but if there is much delay between the RAN and the server, this may bean indication that the signalling performance/throughput bottleneck islocated there and not between the RAN and the terminal device.

In some embodiments of the present disclosure, the first and/or thesecond RTT is estimated S1 and/or S2 by means of packet inspection, e.g.Deep Packet Inspection, DPI.

The communication protocol may be TCP, User Datagram Protocol (UDP) orQuick UDP Internet Connections (QUIC), or any other protocol with acongestion mechanism. A transport protocol can have a mechanism thatdetects how fast it can send data packets. It tries to send more andmore packets, but if there is a lost packet or a packet is not deliveredin time, this is seen as congestion and the protocol backs-off anddecreases the sending rate. UDP does not have congestion mechanism, butTCP and QUIC does.

In accordance with embodiments of the present disclosure it is proposedthat data delivery actions related to available throughput in RAN 2 tothe terminal 4 is based not only on the available throughput but also oninformation on how much RAN nodes 3 contribute to the total end-to-enddelay/RTT or how relevant the RAN throughput information is. Theinformation may either be sent to the terminal device 4, or be used bythe RAN itself. With this information, in relation to estimations oftotal end-to-end RTT, a more correct decision about how to utilize theinformation about the throughput estimations in RAN could be made.

In a similar way as the end-point (i.e. TCP protocol) determines thetotal available end-to-end throughput through RTT measurements, the RTTcontribution between the RAN 2 and the terminal 4, e.g. client 8, ismeasured/estimated by the RAN. There are several methods for estimatingthe RTT between the RAN and the client, and a few examples are givenbelow for completeness of the disclosure.

-   -   The RAN node 3 may perform packet inspection, i.e. DPI, to        determine the first RTT for a packet. The time from a packet        enters the RAN until a corresponding response to the packet is        returned to the RAN may be measured, or    -   The RAN node 3 may monitor the terminal device buffer in the MAC        layer of the RAN, to measure the time from a packet entering the        RAN until leaving the RAN. A generic factor for radio link delay        may then be added. The first RTT may then be estimated as two        times that value.

Through packet inspection, it may be possible for the RAN node 3 todetermine the second RTT, from the RAN to the server 6. By adding up theestimations about the first RTT and the second RTT, the RAN node mayestimate the total end-to-end RTT. By knowing the proportions (i.e.relative contributions) of the first and second RTTs, respectively, therelevance of the estimated throughput on the link between the RAN andthe client may be determined. If the RTT towards the server is thedominating part of the total end-to-end RTT, the relevance of theestimated throughput on the link between the RAN and the client may below and actions for delivery of data should not only, or not at all, bebased on that information.

The actions to be taken based on the information about the RANcontribution to the total end-to-end RTT, may either be performed in theRAN 2 or by the terminal device 4 as the receiver of the informationabout available throughput in the RAN.

-   -   When the RAN node 3 has information about the total end-to-end        RTT, it may also estimate the contribution from the first and/or        second RTT. With this information, the RAN node may make the        decision to send an estimation of throughput to the terminal        device 4 if this information is deemed relevant (i.e. the RAN is        the bottleneck). Otherwise it may decide S7 not to send the        throughput information.    -   If the RAN node estimations of the first and/or second RTT is        sent to the terminal device, the terminal device may compare        this value to its own estimations of end-to-end RTT to determine        if the RAN is the main bottleneck and thereby whether the        estimations of available throughput from RAN are relevant or        not.

The present disclosure has mainly been described above with reference toa few embodiments. However, as is readily appreciated by a personskilled in the art, other embodiments than the ones disclosed above areequally possible within the scope of the present disclosure, as definedby the appended claims.

1. A method performed in a Radio Access Network, RAN, comprised in acommunication network, for locating a communication bottleneck in saidcommunication network, the method comprising: estimating a first RoundTrip Time, RTT, between the RAN and a terminal device connected via theRAN; estimating a second RTT between the RAN and a server of a serviceprovider configured for providing a service to the terminal device viathe RAN; estimating an end-to-end RTT between the terminal device andthe server, based on the first RTT and the second RTT; determining arelative contribution of the second RTT to the end-to-end RTT; anddetermining that the relative contribution of the second RTT indicatesthat signalling performance between the server and the terminal deviceis limited by the signalling performance between the server and the RAN.2. The method of claim 1, wherein the first RTT is estimated between theRAN and a service client in the terminal device.
 3. The method of claim2, wherein the estimating a first RTT comprises estimating a time fromwhen a communication packet for the service client reaches the RAN towhen a response packet, from the service client in response to thecommunication packet, reaches the RAN.
 4. The method of claim 1, whereinthe estimating a second RTT comprises estimating a time from when acommunication packet from the terminal device, for the server, reachesthe RAN to when a response packet from the server, for the terminaldevice, in response to the communication packet, reaches the RAN.
 5. Themethod of claim 1, wherein the determining that the relativecontribution of the second RTT indicates that signalling performancebetween the server and the terminal device is limited by the signallingperformance between the server and the RAN comprises determining that arelative contribution of the first RTT to the end-to-end RTT is below apredetermined first threshold or that the relative contribution of thesecond RTT is above a predetermined second threshold.
 6. The method ofclaim 5, wherein the first threshold is less than 50% or wherein thesecond threshold is at least 50%.
 7. The method of claim 1, furthercomprising: based on the determining that the relative contribution ofthe second RTT indicates that signalling performance between the serverand the terminal device is limited by the signalling performance betweenthe server and the RAN, sending information to the terminal deviceindicating that the signalling performance between the server and theterminal device is limited by the signalling performance between theserver and the RAN.
 8. The method of claim 1, further comprising: basedon the determining that the relative contribution of the second RTTindicates that signalling performance between the server and theterminal device is limited by the signalling performance between theserver and the RAN, deciding not to send information about throughputbetween the RAN and the terminal device to the terminal device.
 9. Themethod of claim 1, wherein the first and/or the second RTT is estimatedusing packet inspection.
 10. The method of claim 1, wherein thesignalling performance comprises signalling throughput.
 11. (canceled)12. A RAN node for a communication network, configured for locating acommunication bottleneck in said communication network, the RAN nodecomprising: processor circuitry; and storage storing instructionsexecutable by said processor circuitry whereby said RAN node isoperative to: estimate a first Round Trip Time, RTT, between the RANnode and a terminal device connected via the RAN node; estimate a secondRTT between the RAN node and a server of a service provider configuredfor providing a service to the terminal device via the RAN node;estimate an end-to-end RTT between the terminal device and the server,based on the first RTT and the second RTT; determine a relativecontribution of the second RTT to the end-to-end RTT; and determine thatthe relative contribution of the second RTT indicates that signallingperformance between the server and the terminal device is limited by thesignalling performance between the server and the RAN.
 13. A computerprogram for locating a communication bottleneck in a communicationnetwork comprising a Radio Access Network, RAN, the computer programcomprising computer program code which is able to, when run on processorcircuitry of a RAN node, cause the RAN node to: estimate a first RoundTrip Time, RTT, between the RAN node and a terminal device connected viathe RAN node; estimate a second RTT between the RAN node and a server ofa service provider configured for providing a service to the terminaldevice via the RAN node; estimate an end-to-end RTT between the terminaldevice and the server, based on the first RTT and the second RTT;determine a relative contribution of the second RTT to the end-to-endRTT; and determine that the relative contribution of the second RTTindicates that signalling performance between the server and theterminal device is limited by the signalling performance between theserver and the RAN.
 14. (canceled)
 15. A non-transitorycomputer-readable storage medium comprising a computer program productincluding instructions to cause at least one processor to: estimate afirst Round Trip Time, RTT, between the RAN and a terminal deviceconnected via a radio access network, RAN; estimate a second RTT betweenthe RAN and a server of a service provider configured for providing aservice to the terminal device via the RAN; estimate an end-to-end RTTbetween the terminal device and the server, based on the first RTT andthe second RTT; determine a relative contribution of the second RTT tothe end-to-end RTT; and determine that the relative contribution of thesecond RTT indicates that signalling performance between the server andthe terminal device is limited by the signalling performance between theserver and the RAN.
 16. The non-transitory computer-readable storagemedium of claim 15, wherein the first RTT is estimated between the RANand a service client in the terminal device.
 17. The non-transitorycomputer-readable storage medium of claim 16, wherein to estimate afirst RTT comprises estimating a time from when a communication packetfor the service client reaches the RAN to when a response packet, fromthe service client in response to the communication packet, reaches theRAN.
 18. The non-transitory computer-readable storage medium of claim15, wherein the estimating a second RTT comprises estimating a time fromwhen a communication packet from the terminal device, for the server,reaches the RAN to when a response packet from the server, for theterminal device, in response to the communication packet, reaches theRAN.
 19. The non-transitory computer-readable storage medium of claim15, wherein to determine that the relative contribution of the secondRTT indicates that signalling performance between the server and theterminal device is limited by the signalling performance between theserver and the RAN comprises determining that a relative contribution ofthe first RTT to the end-to-end RTT is below a predetermined firstthreshold or that the relative contribution of the second RTT is above apredetermined second threshold.
 20. The non-transitory computer-readablestorage medium of claim 19, wherein the first threshold is less than 50%or wherein the second threshold is at least 50%.
 21. The non-transitorycomputer-readable storage medium of claim 15, wherein the instructionsfurther comprise: based on the determining that the relativecontribution of the second RTT indicates that signalling performancebetween the server and the terminal device is limited by the signallingperformance between the server and the RAN, deciding not to sendinformation about throughput between the RAN and the terminal device tothe terminal device.
 22. The non-transitory computer-readable storagemedium of claim 15, wherein the first and/or the second RTT is estimatedusing packet inspection.